General principle and classification of micro sampler (pipette)

General principle and classification of micro sampler (pipette)

The micro sampler first appeared in 1956 and was invented by Schnitger, a scientist at the German Institute of Physiology and Chemistry. Later, in 1958, the German Eppendorf company began to produce button type micro sampler, becoming the world's first micro sampler s company. The pipetting range of these micro-samplers is between 1 and 1000 ~ 1, which is suitable for clinical routine chemistry laboratories. The development of micro-sampler to today, not only is more accurate, but also has a variety of varieties, such as micro-distributor, multi-channel micro-sampler, etc. The physical principles of sample addition are as follows: â‘  use air Sampling by pad (also called piston stroke); â‘¡Pump using positive displacement without air cushion. The above two different principle micro-samplers have different specific application scopes.

First, the piston is moving the sampler

The sampler and dispenser based on the principle of positive piston movement are different from the air cushion sampler due to physical factors. Therefore, in the case where the air cushion sampler is difficult to apply, the piston positive movement sampler can be applied. Such as liquid with high vapor pressure, high viscosity and density greater than 2.0g / cm3; and as in the clinical polymerase chain reaction (PCR) measurement, in order to prevent the generation of aerosol, it is best to use the piston to move the sample Device. The suction head of the piston moving sampler is different from the suction head of the air cushion sampler. It contains a piston that can be coupled to the piston of the sampler. This type of nozzle is generally produced by the piston moving sampler. Manufacturers support the production, can not use the usual tips or tips from different manufacturers.

2. Air cushion sampler

The piston stroke (air cushion) sampler can be conveniently used for sample addition of fixed or adjustable volumes of liquid, with sample volume ranging from less than 1ul to 10ml. The function of the air cushion in the sampler is to separate the liquid sample sucked in the plastic tip from the piston in the sampler. The air cushion moves by the spring-like movement of the sampler piston, which in turn drives the tip The liquid in the liquid, the dead volume and the increase in the height of the pipette tip determine the degree of expansion of this air cushion during sample addition. Therefore, the volume of the piston movement must be about 2% to 4% of the desired volume. The influence of temperature, air pressure and air humidity must be reduced by structural improvements to the air cushion sampler, so that under normal circumstances It will not affect the accuracy of loading. Disposable tips are an important part of the sample addition system, and their shape, material characteristics, and degree of agreement with the sampler have a great influence on the accuracy of sample addition.

Three, multi-channel sampler, electronic sampler and distributor

The principle of the multi-channel sampler, electronic sampler and distributor is the same as above. The multi-channel sampler is usually 8-channel or 12-channel, which is consistent with 8X12 = 96-well microplate. The use of a multi-channel sampler not only reduces the number of sample operations performed by the laboratory operator, but also improves the precision of sample addition. The electronic sampler and distributor are semi-automatic sample adding systems. The biggest advantage of the electronic sampler is that it has a high sample repeatability.

General principle and classification of micro sampler (pipette)